Devices commonly known as “micro-total analysis systems (μTAS)” or “lab-on-chip” comprise a substrate and microstructures such as micro-channels and ports that are provided in the substrate to form channels of specified shapes. It has recently been proposed that a variety of operations such as chemical reaction, synthesis, purification, extraction, generation and/or analysis be performed on substances in the microstructures, and some of the proposals have been commercialized. Structures that are fabricated for this purpose and which have microstructures such as micro-channels and ports provided in the substrate are collectively referred to as “micro-fluid devices” or “micro-channel chips”.
Micro-channel chips find use not only in chemical, biochemical, pharmaceutical, medical and veterinary fields for gene analysis, clinical diagnosis, drug screening and the like but also in a wide range of applications including chemical engineering and environmental monitoring. Compared to devices of the same type in usual size, micro-channel chips have various advantages including (1) extremely smaller amounts of samples and reagents that need to be used, (2) shorter analysis time, (3) higher sensitivity, (4) portability to the site for on-site analysis, and (5) one-way use.
A conventional micro-channel chip is shown in FIGS. 10A and 10B, where it is indicated by numeral 100. As shown, the micro-channel chip 100 comprises an upper substrate 102 that is formed of a material such as a synthetic resin, at least one micro-channel 104 formed in the upper substrate 102, ports 105 and 106 formed in at least one end of the micro-channel 104 to serve as an input port and an output port, and a lower substrate 108 that is adhered to the lower side of the substrate 102 and which is formed of a transparent or opaque material (for example, glass or a synthetic resin film). The lower substrate 108 helps seal the bottoms of the ports 105 and 106, as well as the micro-channel 104. The materials and structures of micro-channel chips of the type shown in FIGS. 10A and 10B, as well as processes for producing them may be found in Patent Documents 1 and 2.
The micro-channels in the micro-channel chip, in order to transfer a fluid (mainly a liquid or gas such as a liquid chemical or sample) from one area to another, occasionally employs a physical or mechanical squeezing means that is applied from the outer surface of the substrate. For example, Patent Document 3 describes a fluid processing device comprising (a) a substrate fixing platform for fixing a substrate formed of an elastic polymeric material having a micro-channel formed in the interior, (b) a solid structure as a pressurizing means that applies pressure from the outside to a surface of the substrate, (c) a linear moving unit as a moving means that is linked to the solid structure or the substrate fixing platform and which moves such solid structure or substrate fixing platform in the longitudinal direction of the micro-channel, and (d) a section that descends the solid structure vertical to the substrate in order to apply pressure to the substrate.
In addition, Patent Document 4 describes a cartridge for biochips that comprises (a) a flat plate of substrate member that is formed of an elastic material and (b) a flexible cover of harder material than the substrate member that is mounted in contact with both the upper and lower surfaces of the substrate member, the substrate member having a sampling section for collecting a biopolymer and a pretreatment section that performs a pretreatment on the biopolymer; according to Patent Document 4, the cover is pressed down by a roll of rigid body for progressively moving the biopolymer from the sampling section toward the pretreatment section.
Furthermore, Patent Document 5 describes a micro-reactor of sheet type in the form of an assembly of flexible sheets that are superposed in intimate contact, which has in its interior (a) a first void section for holding an analyte, (b) a plurality of second void sections communicating with the first void section, and (c) a third void section that communicates with the second void sections and which holds a reagent to perform a chemical reaction with the analyte, further characterized in that a fixed member that serves as a shaft for causing rotation along the surface of the sheet assembly is provided on that surface of the side where the third void section is provided.
Further in addition, Patent Document 6 describes a cartridge for chemical reactions that comprises a vessel at least part of which is formed of an elastic material, the vessel having formed in it a plurality of compartments that are connected or arranged connectable by channels, further characterized in that by applying an external force to the elastic material from the outside of the vessel, a material either in the channel(s) or the compartment(s) or in both is moved to perform a chemical reaction, wherein either the channel(s) or the compartment(s) or both have a capacity of zero before the fluid material is flowed in. In the case of this cartridge, if the fluid material is flowed into the channel(s) and compartment(s), a roller is rolled over the cartridge so as to depress its outer surface, whereby the fluid material is moved in a specified direction.
The problem with the device of Patent Document 3 is that it is extremely difficult to maintain the positional precision while applying a mechanical pressure to the concave channel and no fluid transfer is possible if a positional mismatch occurs. The devices of Patent Documents 4 to 6 are effective for large spaces or channel structures of a simple orientation but they are incapable of complicated squeezing actions such as introducing a liquid chemical through four adjacent ports into the same reaction vessel at different times, or agitating the liquid chemical by reciprocating it at millisecond intervals, or transferring the liquid chemical from one channel to an adjacent channel that is apart by only a few millimeters. In addition, being a mechanical pressurizing means or a transfer means involving centrifugal force, those devices require a moving part, which makes it difficult to sufficiently reduce their size (that they become portable). As a further problem, the physical or mechanical squeezing means is slid over the substrate as it is depressed against the substrate's outer surface, so the substrate is often damaged making it necessary to perform another analysis.    Patent Document 1: Official gazette of JP 2000-27813 A    Patent Document 2: Official gazette of JP 2001-157855 A    Patent Document 3: Specification of Japanese Patent No. 3732159    Patent Document 4: Specification of Japanese Patent No. 3865134    Patent Document 5: Specification of Japanese Patent No. 3746207    Patent Document 6: Official gazette of JP 2005-313065 A